Belt grinder for creating surface structures

ABSTRACT

A workpiece passes through a belt grinder for grinding and structuring a flat workpiece in a predefined direction of passage (P1) past at least one machining area of a structuring device. The structuring device comprises at least one endless grinding belt which is guided over deflection elements in at least one direction of circulation (P3) and the width of the which extends substantially across the working width of the belt grinder, and is guided over deflection elements, the longitudinal axes of which are oriented transversely to the direction of passage (P1) of the workpiece. Furthermore, the structuring device comprises an endless press-on belt  220  which is configured and arranged such that it exerts a force from the inside on the grinding belt in a press-on area, wherein the endless press-on belt is drivable with the aid of a drive unit. The direction of circulation (P2) of the press-on belt runs, at least in the press-on area, transversely to the direction of circulation (P3) of the grinding belt. The structuring device and the transport unit are configured and arranged such that the workpiece guided past the structuring device comes into contact with the machining area of the grinding belt. The structuring device comprises a control unit which controls the drive unit of the press-on belt such that the drive unit selectively drives the endless press-on belt in a first direction of circulation (P2) or in a second direction of circulation that is opposite to the first direction of circulation (P2).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Phase of International Application No. PCT/EP2021/072168, filed Aug. 9, 2021, which claims the benefit of German Application 10 2020 120 968.1, filed Aug. 10, 2020, both of which are incorporated herein in their entireties.

TECHNICAL FIELD

The invention relates to a belt grinder for grinding and structuring a flat workpiece, in which the workpiece passes through the belt grinder in a predefined direction of passage. The belt grinder comprises at least one structuring device for creating surface structures. The structuring device has at least one endless grinding belt guided over deflection elements in at least one direction of circulation and an endless press-on belt which is configured and arranged such that it exerts a force from the inside on the grinding belt in a press-on area, the press-on belt being drivable with the aid of a drive unit.

BACKGROUND

Document DE 10 2004 037 148 C5 discloses a grinding station for a belt grinder with at least one endless grinding belt guided over deflection rollers and a pressure lamella belt circulating within it for pressing the grinding belt against a workpiece. The pressure lamella belt causes an effective grinding process only in those areas in which the pressure lamellae exert a press-on force on the grinding belt in the direction of the workpiece to be machined. As a result, short cuts are produced in the surface of the workpiece to be machined along the pressure lamellae of the pressure lamella belt by the abrasive particles of the grinding belt. The close arrangement of the lamellae of the pressure lamella belt results in a uniform transfer of force from the pressure lamella belt to the grinding belt over the entire working width of the grinding station, so that a uniform grinding pattern without bumps or recesses is achieved.

Document EP 1 530 509 B1 discloses a grinding machine for grinding the surface of a workpiece, comprising oscillating drive means for imparting an oscillating grinding motion to abrasive means. Further, the grinding machine comprises an activation device having a plurality of activation areas controllable in such a manner that alternately different areas of the abrasive can be activated independently of the oscillating grinding motion. The provision and control of the activation areas is relatively complex. The aim is to obtain a surface without directional grinding marks. The oscillating grinding principle produces a circular motion, and the alternating press-on areas are intended to interrupt this circular cutting motion irregularly. These grinding marks cannot be larger than the circular diameter of the circular motion.

Document DE 196 01 379 C2 discloses a device for pressing a circulating grinding belt of a belt grinder against the surface of a workpiece. The device has a pressure beam with a plurality of controllable actuators.

Document US 8,771,037 B2 discloses a grinding device for introducing a specific pattern into a workpiece to be machined. Press-on elements press from the inside against a press-on belt, the press-on elements of which thereby press against the inside of the grinding belt.

Document EP 2 504 125 B1 discloses a device for machining a workpiece in which a carrier element with press-on means is provided which can be driven independently of a circulating machining belt.

Document EP 3 326 750 A1 discloses a grinder for grinding the surface of a workpiece, the grinder having at least one circulating grinding belt and at least one pressure beam for exerting pressure on the grinding belt. A plate is arranged between the grinding belt and the pressure beam, which plate is movably mounted in a plane arranged perpendicular to the direction of the exertable pressure. The plate is provided with elevations, the arrangement of which is free. Due to this punctual arrangement, the grinding forces are also transmitted irregularly and create an irregular deep structure. Lateral movement is also highly restricted by the described solution.

However, for some applications it is desirable to incorporate structures into the surface of a workpiece to be machined in order to obtain a desired surface structure deviating from a flat surface of the workpiece. This surface structure should be creatable over the entire working width of a belt grinder with a simple design of the belt grinder.

Starting therefrom, it is the object of the invention to specify a belt grinder that can also create continuous surface structures over the entire working width. These surface structures can preferably be straight or wavy.

BRIEF DESCRIPTION

This object is solved by a belt grinder having the features of claim 1. Advantageous developments are specified in the dependent claims.

In particular in that the press-on belt is drivable in a first direction of circulation and in a second direction of circulation opposite to the first direction of circulation, and in that the direction of circulation of the press-on belt runs transversely to the direction of circulation of the grinding belt at least in the press-on area, different surface structures can be created with the aid of such a structuring device when machining a workpiece. In particular, an uneven and profiled surface of the workpiece can be created thereby. Preferably, tracks can be ground into the surface of the workpiece to be machined. For this purpose, the press-on elements can exert a punctual force on the grinding belt. In this way, a force can be exerted on the grinding belt from the inside so that continuous surface structures can be created over the entire working width of the workpiece.

At least in the press-on area, the press-on belt comprises at least one press-on element, preferably at least one arrangement with several press-on elements, each of which exerts a press-on force on the inner side of the grinding belt in the direction of a workpiece to be machined. The press-on area is generally the area of the press-on belt in which the press-on elements of the press-on belt exert a force on the inner side of the grinding belt. Each of the press-on elements located in the press-on area exerts a force from the inside on the grinding belt in the direction of a workpiece to be machined at points or on an area whose longest dimension is smaller than the width of the press-on belt in each case, at least when a pressure element of a pressure beam is activated and the area of the press-on belt with the press-on element is located between the pressure element and the grinding belt. The pressure beam comprises several individually controllable and activatable pressure elements arranged one behind the other in the direction of circulation of the press-on belt, so that the press-on area of all pressure elements preferably extends over the entire working width of the structuring device. This makes it particularly easy to exert a force from the inside on the grinding belt so that continuous surface structures can be created over the entire working width of the workpiece.

The press-on elements preferably have a spherical shape. Alternatively or additionally, the press-on elements are arranged symmetrically with respect to at least one axis of symmetry, wherein the axis of symmetry runs in the direction of circulation of the press-on belt and/or transversely to the direction of circulation of the press-on belt.

It is particularly advantageous if a control unit optionally controls the drive unit such that it moves the press-on belt back and forth according to a first drive pattern or that it moves the press-on belt back and forth according to a second drive pattern. This makes it easy to create different surface structures.

Furthermore, it is advantageous if the press-on belt has a first section with a first arrangement of press-on elements and a second section with a second arrangement of press-on elements. This makes it possible to create different surface structures in a simple manner.

When controlling the drive unit for moving the press-on belt with different drive patterns with the aid of a control unit and when providing at least two sections with different arrangements of press-on elements, a variety of different surface structures can be created.

The press-on belt is designed and arranged such that it exerts a force from the inside on the grinding belt in a press-on area. The inside of the endless grinding belt is the side of the grinding belt that contacts the deflection elements through which the endless grinding belt is guided. The inside of the endless grinding belt is thus the side on which no abrasive material is arranged, i.e. the opposite side or rear side of the side of the endless grinding belt that is provided with abrasive material.

It is particularly advantageous if the first arrangement of press-on elements comprises first press-on elements and the second arrangement of press-on elements comprises second press-on elements different from the first press-on elements. Alternatively or additionally, the first arrangement may comprise press-on elements in a first arrangement and the second arrangement may comprise press-on elements in a second arrangement. In particular, the press-on elements can be arranged in a fixed or detachable manner on the press-on belt and, if necessary, can be elastically deformed when a corresponding force is applied. In this way, a desired press-on effect can be easily set in a simple manner. Furthermore, elastically deformable press-on elements in particular are robust and can easily adapt to the contours of workpieces to be machined and also lead to desired grinding results in the area of edges of the workpiece.

It is particularly advantageous if the first arrangement of press-on elements and the second arrangement of press-on elements comprise the same press-on elements. The density of the press-on elements and/or the structure of the arrangement of the press-on elements in the first section and in the second section are then different, so that in the press-on area different forces or forces at different points are exerted on the grinding belt from the inside, depending on whether the press-on elements of the first section or the press-on elements of the second section exert a force on the grinding belt from the inside.

The press-on elements of the respective arrangement can in particular comprise circular, oval and/or rectangular pressure pieces. With the aid of such press-on elements, desired surface structures can be easily created. Furthermore, such press-on elements can be formed very robustly.

It is particularly advantageous if the first section and the second section are arranged one behind the other in the direction of motion or longitudinal direction of the press-on belt. This makes it easy to change the effective press-on areas. A continuous or discontinuous drive of the press-on belt is also possible, so that alternately the first press-on area or the second press-on area exerts a force from the inside on the grinding belt, so that alternately different surface structures can be created.

It is also advantageous if the press-on belt can be driven with the aid of the drive unit in a first direction of circulation and in an opposite second direction of circulation. The press-on belt can be driven continuously or moved back and forth. The back and forth movement can take place with a presettable amplitude and/or presettable frequency. In this way, a desired surface structure can be created in conjunction with the press-on elements of the first section and of the second section in conjunction with the grinding belt.

Furthermore, it is advantageous if the control unit optionally controls the drive unit such that only the first section or only the second section or alternately the first and the second section or at least partially simultaneously the first and the second or parts of the first and parts of the second section or several first and several second sections of the press-on belt press against the grinding belt from the inside. This provides a simple means of selectively creating a variety of different surface structures on the workpiece to be machined.

Furthermore, other sections can be provided in addition to the first section and the second section, which also have different press-on characteristics. In particular, a third and a fourth section can be provided.

Furthermore, it is advantageous if there is a continuous change in the shape, size and/or spacing of the press-on elements along the circumference of the press-on belt. As a result, at least two sections of the press-on belt have different arrangements of press-on elements. By continuously changing the shape, size and/or spacing of the press-on elements along the circumference of the press-on belt, a continuous change in the surface structure that can be created on a workpiece can be easily achieved.

It is also advantageous if the press-on belt is guided over at least two deflection elements, preferably around at least two deflection rollers. This enables simple and reliable guidance of the press-on belt. It is particularly advantageous if the drive unit drives at least one of the deflection rollers for driving the press-on belt. This enables a simple and space-saving design of the structuring device.

It is also advantageous if the drive unit for driving the press-on belt is a first drive unit and if the structuring device has a second drive unit for driving the grinding belt. This enables independent control of the grinding belt and the press-on belt.

Furthermore, it is advantageous if the deflection elements around which the endless grinding belt is guided are deflection rollers, the endless grinding belt preferably being guided over at least three deflection rollers. This enables a simple and robust design of the structuring device.

Furthermore, it is advantageous if a sliding layer is arranged between the press-on belt and the endless grinding belt.

Furthermore, it is advantageous if the structuring device is designed as a belt grinding station with a wide grinding belt circulating parallel to the direction of passage of the workpiece, the width of which extends essentially over the working width of the belt grinding machine and is guided over deflection elements directed transversely to the direction of passage of the workpiece. This allows a simple design of the entire belt grinder.

Furthermore, it is advantageous if the structuring device comprises at least one pressure beam by means of which a force can be exerted on the press-on belt from the inside in the direction of the grinding belt. This allows a predetermined press-on force to be exerted on the press-on belt, so that the press-on belt exerts a predetermined press-on force on at least part of the press-on area on the inside of the grinding belt.

It is particularly advantageous if, at least when a pressure element of the pressure beam is activated, the press-on belt exerts a force from the inside on the grinding belt at least in a part of the press-on area, wherein the pressure beam comprises several individually controllable pressure elements arranged one behind the other in the direction of circulation of the press-on belt, which can be activated when appropriately controlled to generate a press-on force in the press-on area. In this way, parts of the press-on area can be individually and specifically subjected to a press-on force.

Furthermore, it is particularly advantageous if the pressure elements can be controlled such that the press-on elements of the press-on belt arranged between a controlled pressure element and the grinding belt exert a press-on force on the inside of the grinding belt. This makes it possible to introduce specific patterns in areas of the surface of the workpiece to be machined.

It is also advantageous if the press-on belt comprises press-on elements arranged in several rows next to each other in the direction of circulation.

Preferably, the press-on elements in the press-on area generate a press-on force in a press-on element pressure area. The distance between two adjacent press-on elements is selected in particular such that no force or only a small force is transmitted from the press-on belt to the grinding belt between the press-on element pressure areas of these press-on elements. This means that an uneven surface can be created.

It is also advantageous to arrange press-on elements on the press-on belt in a continuous pattern over the entire working width. This makes it possible, for example, to create surface structures with oblique lines.

The press-on elements can be arranged symmetrically to an axis in the direction of circulation of the press-on belt or at least one axis transverse to the direction of circulation of the press-on belt.

Furthermore, the press-on elements can be designed and arranged such that force is transmitted to the inside of the grinding belt in punctual press-on areas.

The effective press-on areas of the press-on elements are preferably at most large enough to create a still visible grinding result, i.e. a delimited pattern visible in the grinding result on the workpiece through the press-on element, and thus not a flat grinding result.

Furthermore, the structuring device can create oscillation tracks as a surface structure on the surface of the workpiece to be machined, in particular by creating a visible, delimited pattern by at least one press-on element on the surface of the workpiece and moving the press-on belt back and forth with the aid of the drive unit for driving the press-on belt. In particular, a pattern symmetrical to the direction of circulation of the grinding belt can be created on the surface of the grinding belt.

Furthermore, a sensor unit can be provided for workpiece detection, wherein a control unit then controls the pressure elements of the pressure beam depending on a signal from the sensor unit.

In general, the structuring device can be designed such that the surface of the workpiece machined with the aid of the structuring device has a non-planar grinding result, which in particular approximates a non-planar grinding.

Further features and advantages result from the following description, which explains embodiments in more detail in connection with the attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective illustration of a belt grinder with a structuring device configured as a grinding station according to an exemplary embodiment.

FIG. 2 shows a schematic top view of an arrangement for machining flat workpieces with a belt grinder according to FIG. 1 .

FIG. 3 shows a simplified schematic illustration of an arrangement for driving and guiding a press-on belt for use in the belt grinder according to FIG. 1 .

FIG. 4 shows a top view of a press-on belt according to a first embodiment, said press-on belt being separated along the separating line A-A in FIG. 3 .

FIG. 5 shows a top view of a press-on belt according to a second embodiment, said press-on belt being separated along the separating line A-A in FIG. 3 .

FIG. 6 shows a top view of a press-on belt according to a third embodiment, said press-on belt being separated along the separating line A-A in FIG. 3 .

FIG. 7 shows a top view of a press-on belt according to a fourth embodiment, said press-on belt being separated along the separating line A-A in FIG. 3 .

FIG. 8 shows a top view of a press-on belt according to a fifth embodiment, said press-on belt being separated along the separating line A-A in FIG. 3 .

FIG. 9 shows a top view of a press-on belt according to a sixth embodiment, said press-on belt being separated along the separating line A-A in FIG. 3 .

FIG. 10 shows a top view of a press-on belt according to a seventh embodiment, said press-on belt being separated along the separating line A-A in FIG. 3 .

FIG. 11 shows a top view of a press-on belt according to a eighth embodiment, said press-on belt being separated along the separating line A-A in FIG. 3 .

FIG. 12 shows a top view of a press-on belt according to a ninth embodiment, said press-on belt being separated along the separating line A-A in FIG. 3 .

FIG. 13 shows a top view of a press-on belt according to a tenth embodiment, said press-on belt being separated along the separating line A-A in FIG. 3 .

FIG. 14 shows a sectional view of a first version of an individual press-on element and a section of the press-on belt according to the first embodiment of FIG. 4 .

FIG. 15 shows a sectional view of a second version of an individual press-on element and a section of the press-on belt according to the first embodiment of FIG. 4 .

FIG. 16 shows a sectional view of a third version of an individual press-on element and a section of the press-on belt according to the first embodiment of FIG. 4 .

FIG. 17 shows a sectional view of a fourth version of an individual press-on element and a section of the press-on belt according to the first embodiment of FIG. 4 .

FIG. 18 shows a sectional view of a fifth version of an individual press-on element and a section of the press-on belt according to the first embodiment of FIG. 4 ; and

FIG. 19 shows a sectional view of a sixth version of an individual press-on element and a section of the press-on belt according to the first embodiment of FIG. 4 .

DETAILED DESCRIPTION

FIG. 1 shows a perspective illustration of a belt grinder 100 with a structuring device 200 designed as a grinding station according to one embodiment. In addition to the structuring device 200, the belt grinder 100 comprises a conveyor belt 110 which is guided around two deflection rollers 112, 114 and which guides the workpieces 10 to be machined with the aid of the structuring device 200 in the direction of the arrow P1 past a machining area of the structuring device 200. The structuring device 200 comprises an endless grinding belt 210 which is guided around three deflection rollers 212, 214, 216. In other embodiments, only two deflection rollers or more than three deflection rollers may be provided. Alternatively, other deflection elements, such as deflection plates, may be provided instead of the deflection rollers 212, 214, 216.

A press-on belt 220 guided over deflection rollers 222, 224 is arranged inside the endless grinding belt 210, press-on elements being formed on the circumferential surface of the press-on belt 220, the press-on elements having a first size in a first section 230 and being arranged in a first arrangement and having a second size in a second section 240 and being arranged in a second arrangement. A press-on element of the first section 230 is identified with the reference numeral 232, and a press-on element of the second section 240 is identified with the reference numeral 242.

To drive the press-on belt 220, in the present embodiment the deflection roller 224 is drivable with the aid of a first drive unit. In other embodiments, the other deflection roller 222, another deflection roller or both deflection rollers 222, 224 may also be drivable. With the aid of the first drive unit, the press-on belt 220 can be driven either in the direction of circulation P2 or opposite to the direction of circulation P2, depending on the control of the first drive unit. This also allows the press-on belt 220 to be moved back and forth to create different surface structures. A sliding layer 250 is arranged between the press-on belt 220 and the inner side 211 of the endless grinding belt 210, which reduces friction compared to a direct contact of the press-on belt 220 with the inner side 211 of the endless grinding belt 210. This reduces in particular the abrasion on the inner side of the grinding belt 210 and the associated wear of the grinding belt 210. The press-on elements 232, 242 of the press-on belt 220 press against the inner side 211 of the grinding belt 210 in a press-on area, wherein the sliding layer 250 may be arranged between the press-on elements 232, 242 and the inner side 211 of the grinding belt 210. In other embodiments, no sliding layer 250 is provided. In this case, the press-on area comprises the area of the inner side 211 of the grinding belt 220 that is arranged opposite the press-on belt 220. Two corner points of the press-on area or surface are identified in FIG. 1 with reference signs 226 and 227, and the press-on area is identified with the reference sign 229.

Depending on the structure, shape and size of the press-on elements 232, 242 of the different sections 230, 240 and by a drive of the press-on belt 220, different surface structures can be created during grinding of the workpiece 10.

The structuring device 200 comprises a second drive unit for driving the endless grinding belt 210 in a direction of circulation P3 and/or opposite to the direction of circulation P3. Preferably, this second drive unit is used to drive one of the deflection rollers 212, 214 and/or 216.

The structuring device 200 according to the first embodiment is a longitudinal structuring device, in which the direction of circulation P3 of the grinding belt 210 in the press-on area 229 of the press-on belt 220 runs parallel to the transport direction P1 of the workpiece 10, i.e. the direction of circulation P3 of the grinding belt 210 in the press-on area 229 of the press-on belt 220 is in or opposite to the transport direction P1 of the workpiece 10.

The structuring device 200 comprises at least one pressure beam 300, which is preferably connected to a frame of the structuring device 200 that is not shown and which comprises a plurality of pressure elements 310, 312 that are arranged one behind the other in the direction of circulation P2 of the press-on belt 220. In particular, the pressure beam 300 is arranged between the deflection rollers 222 and 224. The pressure beam 300 can exert a force from the inside on the press-on belt 220 in the direction of the grinding belt 210. In particular, the individual pressure elements 310, 312 of the pressure beam 300 can exert a predetermined press-on force on the press-on belt 220 so that the press-on belt 220 or the press-on elements 232, 242 exert a predetermined press-on force on at least a part of the press-on area 229 on the inner side 211 of the grinding belt 210.

When at least one pressure element 310, 312 of the pressure beam 300 is activated, it presses the press-on belt 220 at least in a part of the press-on area 229 with a predetermined force against the inner side 211 of the grinding belt 210. The pressure elements 310, 312 can be controlled individually so that, when controlled accordingly, they exert a press-on force in the part of the press-on area 229 opposite the pressure element on the press-on belt 220 and the press-on elements 232, 242 located in the area of the controlled pressure element 310, 312. In this way, a part of the press-on elements 232, 242 can be individually and selectively subjected to a press-on force and exert corresponding press-on forces in the press-on area 229 on the grinding belt 210.

In particular, the pressure elements 310, 312 can be controlled by a control unit such that the press-on elements 232, 242 of the press-on belt 220, which are present between a controlled pressure element 310, 312 and the grinding belt 210, exert a force on the inner side 211 of the grinding belt 210. This allows specific desired patterns to be introduced in areas of the surface of the workpiece 10 to be machined. The pressure elements 310, 312 and the pressure beam 300 can in particular be constructed and/or controlled as disclosed in document DE 196 01 379 C2.

FIG. 2 shows a schematic top view of an arrangement 500 for machining flat workpieces 10. The arrangement 500 comprises the belt grinder 100 with the conveyor unit designed as a conveyor belt 110 for transporting the workpiece 10 in the direction of the arrow P1 past the structuring device 200 for machining the workpiece 10. In the transport direction P1 prior to the structuring device 200, i.e. upstream of the structuring device 200, a sensor unit 520 is arranged to detect at least the arrival of the leading edge of the workpiece 10 and to generate at least one corresponding sensor information. In other embodiments, the sensor unit 520 may additionally or alternatively detect the side edges and the rear edge of the workpiece 10. The generated sensor information is transmitted to the control unit 510, which then controls the drive units of the pressure elements 310, 320 of the pressure beam 300 depending on the signal of the sensor unit 520 and/or depending on the desired surface structure to be created on the surface of the workpiece to be machined.

In this context, the sensor unit 520 may comprise light barriers, light scanners, laser distance measuring units, at least one camera, preferably a line scan camera, at least one inductive sensor and/or at least one reed contact, mechanical switches, in particular switch rollers, ultrasonic sensors, in particular ultrasonic distance measuring sensors. Preferably, the sensor unit 520 is configured to detect any shape and/or position of the workpiece 10. Based on this, the control unit 510 can select specific areas and individually control the drive units of the pressure elements 310, 312.

In other embodiments, the provision of the sensor unit 520 can also be dispensed with if the geometry of the workpiece 10 is determined by inputting and/or transmitting corresponding data to the control unit 510. It is particularly advantageous if the sensor unit 520 determines the course of the surface of the workpiece 14 to be machined in the detection area of the sensor unit 520, for example, with the aid of a plurality of laser distance measuring units, the respective detection area subsequently corresponding to a machining area in the transport direction P1. This enables simple and precise control of the pressure elements 310, 312 as a function of the course of the surface to be machined in the corresponding machining area, which is detected with the aid of the sensor unit 520.

FIG. 3 shows a simplified schematic illustration of an arrangement for driving and guiding the press-on belt 220 for use in a structuring device 200 according to FIG. 1 . The endless press-on belt 220 guided around the deflection rollers 222, 224 is separated along the separating line A-A in the following FIGS. 4 to 13 , FIGS. 4 to 13 each showing a top view of the outer surface of the separated press-on belt 220 according to twelve different embodiments.

FIG. 4 shows a top view of a separated press-on belt 220 according to a first embodiment, wherein the press-on belt 220 according to the first embodiment corresponds to the press-on belt 220 shown in FIGS. 1 and 2 . In the first section 230, the protruding circular press-on elements 232 have a first diameter and are each arranged in three rows below one another, with the columns having the same spacing as the rows. In the second section 240, the protruding circular press-on elements 242 have a smaller second diameter than the press-on elements 232 in the first section 230 and are arranged in four rows one below the other, with the columns having the same spacing as the rows.

FIG. 5 shows a top view of a separated press-on belt 220 according to a second embodiment in which all press-on elements 232, 242 have the same diameter and are each arranged in three rows with the same row spacing relative to one another, the column spacing decreasing continuously from area 230 towards area 240 or increasing continuously from area 240 towards area 230.

FIG. 6 shows a top view of a separated press-on belt 220 according to a third embodiment, in which a plurality of first sections 230 and a plurality of second sections 240 are arranged one behind the other in the direction of circulation P2.

FIG. 7 shows a top view of a separated press-on belt 220 according to a fourth embodiment, which corresponds to the first embodiment according to FIG. 4 in the arrangement of the press-on elements 232, 242, wherein the press-on elements 232, 242, in contrast to the first embodiment, do not have a circular head but an oval head.

FIG. 8 shows a top view of a separated press-on belt 220 according to a fifth embodiment, which corresponds to the second embodiment according to FIG. 5 in the arrangement of the press-on elements 232, 242 and differs in the shape of the press-on head of the press-on element 232, 242, wherein the press-on elements 232, 242 do not have a circular head but an oval head.

FIG. 9 shows a top view of a separated press-on belt 220 according to a sixth embodiment. The arrangement of the press-on elements 232, 242 according to the sixth embodiment is the same as the arrangement of the press-on elements 232, 242 of the third embodiment. However, in the sixth embodiment, oval press-on elements 232, 242 are provided instead of circular press-on elements 232, 242.

FIG. 10 shows a top view of a separated press-on belt 220 according to a seventh embodiment, wherein the arrangement of the press-on elements 232, 242 of the seventh embodiment is the same as those of the first embodiment, wherein square press-on elements 232, 242 are provided instead of circular press-on elements 232, 242.

FIG. 11 shows a top view of a separated press-on belt 220 according to an eighth embodiment. The arrangement of the press-on elements 232, 242 is the same as the arrangement of the press-on elements 232, 242 of the second embodiment according to FIG. 5 , with square press-on elements 232, 242 being used instead of the circular press-on elements 232, 242.

FIG. 12 shows a top view of a separated press-on belt 220 according to a ninth embodiment. The arrangement of the press-on elements 232, 242 corresponds to the arrangement of the press-on elements 232, 242 of the third embodiment according to FIG. 6 , with square press-on elements being used instead of circular press-on elements.

FIG. 13 shows a top view of a separated press-on belt 220 according to a tenth embodiment. In the first section 230, the press-on elements 232 are arranged in a first pattern and have a first size and in the second section 240, the press-on elements 242 are arranged in a second pattern and have a second size.

FIG. 14 shows a sectional view of a single press-on element 232, 242 and a section of the press-on belt 220 according to the first embodiment according to FIG. 4 , wherein the press-on elements 232, 234 are formed as cones.

FIG. 15 shows a sectional view of a second version of a press-on element 232, 244 and a section of the press-on belt 220 according to the first embodiment according to FIG. 4 , wherein the press-on element 232, 242 has a convex cross-section. In other embodiments, the press-on element 232, 242 may also be a spherical segment.

FIG. 16 shows a sectional view of a third version of a single press-on element 232, 242 of the press-on belt 220 according to the first embodiment of FIG. 4 . In contrast to the first two versions, the press-on element 232, 242 is cylindrical.

FIG. 17 shows a sectional view of a fourth version of a single press-on element 232, 242 and a section of the press-on belt 220 according to the first embodiment according to FIG. 4 , wherein the press-on element 232, 242 according to the first version according to FIG. 14 is connected to the press-on belt 220 via an additional rod-shaped element 233, 243. The head of the press-on element 232, 242 according to FIG. 17 corresponds to the press-on element 232, 242 according to the first version according to FIG. 14 .

FIG. 18 shows a sectional view of a fifth version of a single press-on element 232, 242 and a section of the press-on belt 220 according to the first embodiment according to FIG. 4 , wherein the press-on element 232, 242 is connected to the press-on belt 220 via a rod-shaped element 233, 243 and otherwise corresponds to the press-on element 232, 242 according to the second version.

FIG. 19 shows a sectional view of a sixth version of a single press-on element 232, 242 and a section of the press-on belt 220 according to the first embodiment according to FIG. 4 . The press-on element 232, 242 is connected to the press-on belt 220 via a rod-shaped element 233, 243 and otherwise corresponds to the third version according to FIG. 16 .

By connecting the press-on elements 232, 242 via a rod-shaped element 233, 243 to the press-on belt 220, the respective press-on element 232, 242 can be pivoted by elastic deformation of the rod-shaped element 233, 243 when force is applied and can adapt to the contours of the workpiece 10 to be machined.

Both in the first section 230 and in the second section 240 of the press-on belt 220, different press-on elements 232, 242 can be combined with each other, which differ from each other both in shape and in size. A mixed arrangement of circular press-on elements 232, 242, square press-on elements 232, 242 or oval press-on elements 232, 242 is also possible, wherein the individual press-on elements 232, 242 can differ from one another both in shape and in size. The press-on elements shown in FIGS. 14 to 19 relate to the circular press-on elements 232, 242 shown in FIGS. 4, 5, 6, 13 . The oval press-on elements 232, 242 shown in FIGS. 7, 8 and 9 may have the cross-sections shown in FIGS. 14 to 19 . Similarly, the square press-on elements 232, 242 shown in FIGS. 10 to 12 may have the cross-sections shown in FIGS. 14 to 19 . 

What is claimed is:
 1. A belt grinder for grinding and structuring a flat workpiece, in which the workpiece passes through the belt grinder in a predetermined direction of passage (P1), with at least one structuring device; with at least one transport unit for the transport of the workpiece in the direction of passage (P1) past a machining area of the structuring device, the structuring device comprising: at least one endless grinding belt guided over deflection elements in at least one direction of circulation (P3), the width of which substantially extending over the working width of the belt grinder and being guided over deflection elements, the longitudinal axes of which are directed transversely to the direction of passage (P1) of the workpiece, an endless press-on belt configured and arranged such that is exerts a force from the inside on the grinding belt in a press-on area, the endless press-on belt being drivable with the aid of a drive unit, the direction of circulation (P2) of the press-on belt runs transversely to the direction of circulation (P3) of the grinding belt at least in the press-on area, wherein the structuring device and the transport unit are configured and arranged such that the workpiece guided past the structuring device is contacted by the machining area of the grinding belt, characterized in that the structuring device comprises a control unit which controls the drive unit of the press-on belt such that the drive unit drives the endless press-on belt optionally in a first direction of circulation (P2) or in a second direction of circulation opposite to the first direction of circulation (P2).
 2. The belt grinder according to claim 1, characterized in that the control unit of the structuring device optionally controls the drive unit such that it moves the press-on belt back and forth according to a first drive pattern or that it moves the press-on belt back and forth according to a second drive pattern.
 3. The belt grinder according to claim 1, characterized in that the press-on belt of the structuring device has a first section with a first arrangement of press-on elements and at least one second section with a second arrangement of press-on elements.
 4. The belt grinder according to claim 3, characterized in that the first arrangement of press-on elements comprises first press-on elements and the second arrangement of press-on elements comprises second press-on elements different from the first press-on elements and/or that the first arrangement of press-on elements comprises press-on elements in a first arrangement and the second arrangement of press-on elements comprises press-on elements in a second arrangement.
 5. The belt grinder according to claim 3, characterized in that the first arrangement of press-on elements and the second arrangement of press-on elements comprise the same press-on elements, the density of the press-on elements and/or the structure of the arrangement of the press-on elements in the first section and in the second section being different.
 6. The belt grinder according to claim 3, characterized in that the first section and the second section are arranged behind one another in the direction of motion of the press-on belt.
 7. The belt grinder according to claim 3, characterized in that the control unit of the structuring device controls the drive unit for driving the press-on belt optionally such that only the first section or that only the second section or alternately the first and the second section or at least partially simultaneously the first and the second section or parts of the first and parts of the second section or several first and several second sections of the press-on belt press against the grinding belt from the inside.
 8. The belt grinder according to claim 3, characterized in that the shape, the size and/or the spacing of the press-on elements continuously changes along the circumference of the press-on belt.
 9. The belt grinder according to claim 1, characterized in that the press-on belt is guided over at least two deflection elements, preferably around at least two deflection rollers and that the drive unit drives at least one deflection roller for driving the press-on belt.
 10. The belt grinder according to claim 1, characterized in that the deflection elements of the structuring device are deflection rollers, the endless grinding belt preferably being guided over at least three deflection rollers.
 11. The belt grinder according to claim 1, characterized in that between the press-on belt and the endless grinding belt a sliding layer is arranged.
 12. The belt grinder according to claim 1, characterized in that the structuring device comprises at least one pressure beam, by which a force can be exerted from the inside onto the press-on belt in the direction of the grinding belt.
 13. The belt grinder according to claim 12, characterized in that the press-on belt exerts a force from the inside on the grinding belt at least in a part of the press-on area at least when a pressure element of the pressure beam is activated, the pressure beam comprising several individually controllable pressure elements arranged behind one another in the direction of circulation (P2) of the press-on belt, which pressure elements are activatable, when controlled accordingly, for generating a press-on force in the press-on area.
 14. The belt grinder according to claim 12, characterized in that the pressure elements are controllable such that the press-on elements of the press-on belt that are present between a controlled pressure element and the grinding belt exert a force on the inner side of the grinding belt. 